Set-delayed cement compositions comprising pumice and associated methods

ABSTRACT

Disclosed is a method of spraying a surface with a set-delayed cement. The method comprises providing a set-delayed cement composition comprising water, pumice, hydrated lime, and a set retarder; spraying a surface with the set-delayed cement composition; and allowing the set-delayed cement composition to set on the surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/634,764, entitled “Set-Delayed Cement Compositions ComprisingPumice and Associated Methods,” filed on Feb. 28, 2015, which is acontinuation-in-part of U.S. patent application Ser. No. 14/478,869,entitled “Set-Delayed Cement Compositions Comprising Pumice andAssociated Methods,” filed on Sep. 5, 2014, which is a continuation ofU.S. patent application Ser. No. 13/417,001, entitled “Set-DelayedCement Compositions Comprising Pumice and Associated Methods,” filed onMar. 9, 2012, the entire disclosures of which are incorporated herein byreference.

BACKGROUND

Examples relate to cementing operations and, in certain examples, toset-delayed cement compositions and methods of using set-delayed cementcompositions in surface operations.

Cement compositions may be used in a variety of surface operations. Forexample, in spraying application, a cement handling system may spraycement into a pond, creek, or ditch, in order to line the structureswith an impermeable barrier. Similarly, cement may be used to coat otherstructures such as walls, floors, or ceilings in order to providesupport and in some applications, heat resistance. In constructionapplications, cement may be used to stabilize supports in a mine orattached to a pier.

A broad variety of cement compositions have been used in surfacecementing operations. In some instances, set-delayed cement compositionshave been used. Set-delayed cement compositions are characterized bybeing capable of remaining in a pumpable fluid state for at least aboutone day (e.g., at least about 7 days, about 2 weeks, about 2 years ormore) at room temperature (e.g., about 80° F.). When desired for use,the set-delayed cement compositions should be capable of being activatedwhereby reasonable compressive strengths are developed. For example, acement set activator may be added to a set-delayed cement compositionwhereby the composition sets into a hardened mass. Among other things,the set-delayed cement composition may be suitable for use in surfaceapplications, for example, where it is desired to prepare the cementcomposition in advance. This may allow, for example, the cementcomposition to be stored prior to its use. In addition, this may allow,for example, the cement composition to be prepared at a convenientlocation and then transported to the job site. Accordingly, capitalexpenditures may be reduced due to a reduction in the need for on-sitebulk storage and mixing equipment. This may be particularly useful forapplications where space and equipment may be limited.

While set-delayed cement compositions have been developed heretofore,challenges exist with their successful use in surface cementingoperations. For example, set-delayed cement compositions prepared withPortland cement may have undesired gelation issues which can limit theiruse and effectiveness in cementing operations. Other set-delayedcompositions that have been developed, for example, those comprisinghydrated lime and quartz, may be effective in some operations but mayhave limited use at lower temperatures as they may not developsufficient compressive strength when used in applications where lowtemperature may be an issue.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some of the embodiments ofthe present method, and should not be used to limit or define themethod.

FIG. 1 illustrates a system for the preparation of a set-delayed cementcomposition and subsequent delivery of the composition to a cementingapplication site.

FIG. 2 illustrates the use of the set-delayed cement composition in aspray application for a pond.

FIG. 2A illustrates an enlarged perspective of a portion of the exampleillustrated in FIG. 2

FIG. 3 illustrates a marine construction application, wherein aset-delayed cement composition may be pumped through a conduit to securein place a beam to be used in the extension of pier.

FIG. 4 illustrates the use of a set-delayed cement composition in a mineoperation.

DETAILED DESCRIPTION

Examples relate to cementing operations and, in certain examples, toset-delayed cement compositions and methods of using set-delayed cementcompositions in surface operations. In particular examples, theset-delayed cement compositions may be used to line ponds, creeks,ditches, etc. In further examples, the set-delayed cement compositionsmay be used for marine construction, mine construction, or cementoperations necessitating cement spraying. Additional examples maycomprise using the set-delayed cement compositions to coat structures toamongst other reasons, impart heat resistance to the structures.

The set-delayed cement compositions may generally comprise water,pumice, hydrated lime, and a set retarder. Optionally, the set-delayedcement compositions may further comprise a dispersant and/or a cementset activator. The set-delayed cement compositions may be foamed.Advantageously, the set-delayed cement compositions may be capable ofremaining in a pumpable fluid state for an extended period of time. Forexample, the set-delayed cement compositions may remain in a pumpablefluid state for at least about 1 day, about 2 weeks, about 2 years, orlonger. Advantageously, the set-delayed cement compositions may developreasonable compressive strengths after activation at relatively lowtemperatures. While the set-delayed cement compositions may be suitablefor a number of cementing operations, they may be particularly suitablefor use in applications in which alkali silicate reactions occur. Alkalisilicate reactions may crack or deform concrete. The set-delayed cementcompositions described herein may prevent alkali silicate reactions fromoccurring, thus mitigating cracks and deformations in any concrete inwhich the set-delayed cement composition is used.

The water may be from any source provided that it does not contain anexcess of compounds that may undesirably affect other components in theset-delayed cement compositions. For example, a set-delayed cementcomposition may comprise fresh water or salt water. Salt water generallymay include one or more dissolved salts therein and may be saturated orunsaturated as desired for a particular application. Seawater or brinesmay be suitable for use in embodiments. Further, the water may bepresent in an amount sufficient to form a pumpable slurry. In certainexamples, the water may be present in the set-delayed cement compositionin an amount in the range of from about 33% to about 200% by weight ofthe pumice. In certain examples, the water may be present in theset-delayed cement compositions in an amount in the range of from about35% to about 70% by weight of the pumice. One of ordinary skill in theart with the benefit of this disclosure will recognize the appropriateamount of water for a chosen application.

Pumice may be present in the set-delayed cement compositions. Generally,pumice is a volcanic rock that can exhibit cementitious properties inthat it may set and harden in the presence of hydrated lime and water.The pumice may also be ground. Generally, the pumice may have anyparticle size distribution as desired for a particular application. Incertain examples, the pumice may have a mean particle size in a range offrom about 1 micron to about 200 microns. The mean particle sizecorresponds to d50 values as measured by particle size analyzers such asthose manufactured by Malvern Instruments, Worcestershire, UnitedKingdom. In specific examples, the pumice may have a mean particle sizein a range of from about 1 micron to about 200 microns, from about 5microns to about 100 microns, or from about 10 microns to about 50microns. In one particular example, the pumice may have a mean particlesize of less than about 15 microns. An example of a suitable pumice isavailable from Hess Pumice Products, Inc., Malad, Id., as DS-325lightweight aggregate, having a particle size of less than about 15microns. It should be appreciated that particle sizes too small may havemixability problems while particle sizes too large may not beeffectively suspended in the compositions. One of ordinary skill in theart, with the benefit of this disclosure, should be able to select aparticle size for the pumice suitable for a chosen application.

Hydrated lime may be present in the set-delayed cement compositions. Asused herein, the term “hydrated lime” will be understood to mean calciumhydroxide. In some embodiments, the hydrated lime may be provided asquicklime (calcium oxide) which hydrates when mixed with water to formthe hydrated lime. The hydrated lime may be included in the set-delayedcement compositions, for example, to form a hydraulic composition withthe pumice. The hydrated lime may be included in apumice-to-hydrated-lime weight ratio of about 10:1 to about 1:1 or 3:1to about 5:1. Where present, the hydrated lime may be included in theset-delayed cement compositions in an amount in the range of from about10% to about 100% by weight of the pumice. In some examples, thehydrated lime may be present in an amount ranging between any of and/orincluding any of about 10%, about 20%, about 40%, about 60%, about 80%,or about 100% by weight of the pumice. In some examples, thecementitious components present in the set-delayed cement compositionmay consist essentially of the pumice and the hydrated lime. Forexample, the cementitious components may primarily comprise the pumiceand the hydrated lime without any additional components (e.g., Portlandcement, fly ash, slag cement) that hydraulically set in the presence ofwater. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of the hydrated limeto include for a chosen application.

A set retarder maybe present in the set-delayed cement compositions. Abroad variety of set retarders may be suitable for use in theset-delayed cement compositions. For example, the set retarder maycomprise phosphonic acids, such as ethylenediamine tetra(methylenephosphonic acid), diethylenetriamine penta(methylene phosphonic acid),etc.; lignosulfonates, such as sodium lignosulfonate, calciumlignosulfonate, etc.; salts such as stannous sulfate, lead acetate,monobasic calcium phosphate, organic acids, such as citric acid,tartaric acid, etc.; cellulose derivatives such as hydroxyl ethylcellulose (HEC) and carboxymethyl hydroxyethyl cellulose (CMHEC);synthetic co- or ter-polymers comprising sulfonate and carboxylic acidgroups such as sulfonate-functionalized acrylamide-acrylic acidco-polymers; borate compounds such as alkali borates, sodium metaborate,sodium tetraborate, potassium pentaborate; derivatives thereof, ormixtures thereof. Examples of suitable set retarders include, amongothers, phosphonic acid derivatives. One example of a suitable setretarder is Micro Matrix® cement retarder, available from HalliburtonEnergy Services, Inc. Generally, the set retarder may be present in theset-delayed cement compositions in an amount sufficient to delay thesetting for a desired time. In some examples, the set retarder may bepresent in the set-delayed cement compositions in an amount in the rangeof from about 0.01% to about 10% by weight of the pumice. In specificexamples, the set retarder may be present in an amount ranging betweenany of and/or including any of about 0.01%, about 0.1%, about 1%, about2%, about 4%, about 6%, about 8%, or about 10% by weight of the pumice.One of ordinary skill in the art, with the benefit of this disclosure,will recognize the appropriate amount of the set retarder to include fora chosen application.

As previously mentioned, examples of the set-delayed cement compositionsmay optionally comprise a dispersant. Examples of suitable dispersantsinclude, without limitation, sulfonated-formaldehyde-based dispersants(e.g., sulfonated acetone formaldehyde condensate), examples of whichmay include Daxad® 19 dispersant available from Geo Specialty Chemicals,Ambler, Pa. Other suitable dispersants may be polycarboxylated etherdispersants such as Liquiment® 5581F and Liquiment® 514L dispersantsavailable from BASF Corporation Houston, Tex.; or Ethacryl™ G dispersantavailable from Coatex, Genay, France. An additional example of asuitable commercially available dispersant is CFR™-3 dispersant,available from Halliburton Energy Services, Inc., Houston, Tex. TheLiquiment® 514L dispersant may comprise 36% by weight of thepolycarboxylated ether in water. While a variety of dispersants may beused, polycarboxylated ether dispersants may be particularly suitablefor use. Without being limited by theory, it is believed thatpolycarboxylated ether dispersants may synergistically interact withother components of the set-delayed cement composition. For example, itis believed that the polycarboxylated ether dispersants may react withcertain set retarders (e.g., phosphonic acid derivatives) resulting information of a gel that suspends the pumice and hydrated lime in thecomposition for an extended period of time.

The dispersant may be included in the set-delayed cement compositions inan amount in the range of from about 0.01% to about 5% by weight of thepumice. In specific examples, the dispersant may be present in an amountranging between any of and/or including any of about 0.01%, about 0.1%,about 0.5%, about 1%, about 2%, about 3%, about 4%, or about 5% byweight of the pumice. One of ordinary skill in the art, with the benefitof this disclosure, will recognize the appropriate amount of thedispersant to include for a chosen application.

When desired for use, the set-delayed cement compositions may beactivated (e.g., by combination with an activator) to set into ahardened mass. The term “cement set activator” or “activator”, as usedherein, refers to an additive that activates a set-delayed or heavilyretarded cement composition and may also accelerate the setting of theset-delayed, heavily retarded, or other cement composition. By way ofexample, the set-delayed cement compositions may be activated to form ahardened mass in a time period in the range of from about 10 seconds toabout 2 hours. For example, embodiments of the set-delayed cementcompositions may set to form a hardened mass in a time period rangingbetween any of and/or including any of about 10 seconds, about 30seconds, about 1 minute, about 10 minutes, about 30 minutes, about 1hour, or about 2 hours.

One or more cement set activators may be added to the set-delayed cementcompositions. Examples of suitable cement set activators include, butare not limited to: zeolites, amines such as triethanolamine,diethanolamine; silicates such as sodium silicate; zinc formate; calciumacetate; Groups IA and IIA hydroxides such as sodium hydroxide,magnesium hydroxide, and calcium hydroxide; monovalent salts such assodium chloride; divalent salts such as calcium chloride; nanosilica(i.e., silica having a particle size of less than or equal to about 100nanometers); polyphosphates; and combinations thereof. In someembodiments, a combination of the polyphosphate and a monovalent saltmay be used for activation. The monovalent salt may be any salt thatdissociates to form a monovalent cation, such as sodium and potassiumsalts. Specific examples of suitable monovalent salts include potassiumsulfate, and sodium sulfate. A variety of different polyphosphates maybe used in combination with the monovalent salt for activation of theset-delayed cement compositions, including polymeric metaphosphatesalts, phosphate salts, and combinations thereof. Specific examples ofpolymeric metaphosphate salts that may be used include sodiumhexametaphosphate, sodium trimetaphosphate, sodium tetrametaphosphate,sodium pentametaphosphate, sodium heptametaphosphate, sodiumoctametaphosphate, and combinations thereof. A specific example of asuitable cement set activator comprises a combination of sodium sulfateand sodium hexametaphosphate. In a specific example, the activator maybe provided and added to the set-delayed cement composition as a liquidadditive, for example, a liquid additive comprising a monovalent salt, apolyphosphate, and optionally a dispersant.

Some embodiments may include a cement set activator comprisingnanosilica. As used herein, the term “nanosilica” refers to silicahaving a particle size of less than or equal to about 100 nanometers(“nm”). The size of the nanosilica may be measured using any suitabletechnique. It should be understood that the measured size of thenanosilica may vary based on measurement technique, sample preparation,and sample conditions such as temperature, concentration, etc. Onetechnique for measuring the particle size of the nanosilica isTransmission Electron Microscopy (TEM). An example of a commerciallyavailable product based on laser diffraction is the ZETASIZER Nano ZSparticle size analyzer supplied by Malvern Instruments, Worcerstershire,UK. In some examples, the nanosilica may comprise colloidal nanosilica.The nanosilica may be stabilized using any suitable technique. In someexamples, the nanosilica may be stabilized with a metal oxide, such aslithium oxide, sodium oxide, potassium oxide, and/or a combinationthereof. Additionally the nanosilica may be stabilized with an amineand/or a metal oxide as mentioned above. Without limitation by theory,it is believed that the nanosilicas have an additional advantage in thatthey have been known to fill in pore space in cements which can resultin superior mechanical properties in the cement after it has set.

Some examples may include a cement set activator comprising acombination of a monovalent salt and a polyphosphate. The monovalentsalt and the polyphosphate may be combined prior to addition to theset-delayed cement composition or may be separately added to theset-delayed cement composition. The monovalent salt may be any salt thatdissociates to form a monovalent cation, such as sodium and potassiumsalts. Specific examples of suitable monovalent salts include potassiumsulfate and sodium sulfate. A variety of different polyphosphates may beused in combination with the monovalent salt for activation of theset-delayed cement compositions, including polymeric metaphosphatesalts, phosphate salts, and combinations thereof, for example. Specificexamples of polymeric metaphosphate salts that may be used includesodium hexametaphosphate, sodium trimetaphosphate, sodiumtetrametaphosphate, sodium pentametaphosphate, sodiumheptametaphosphate, sodium octametaphosphate, and combinations thereof.A specific example of a suitable cement set activator comprises acombination of sodium sulfate and sodium hexametaphosphate.Interestingly, sodium hexametaphosphate is also known in the art to be astrong retarder of Portland cements. Because of the unique chemistry ofpolyphosphates, polyphosphates may be used as a cement set activator forthe set-delayed cement compositions disclosed herein. The ratio of themonovalent salt to the polyphosphate may range, for example, from about5:1 to about 1:25 or from about 1:1 to about 1:10. In some examples thecement set activator may comprise the monovalent salt and thepolyphosphate salt in a ratio (monovalent salt to polyphosphate) rangingbetween any of and/or including any of about 5:1, 2:1, about 1:1, about1:2, about 1:5, about 1:10, about 1:20, or about 1:25.

In some examples, the combination of the monovalent salt and thepolyphosphate may be mixed with a dispersant and water to form a liquidadditive for activation of a set-delayed cement composition. Examples ofsuitable dispersants include, without limitation, the previouslydescribed dispersants, such as sulfonated-formaldehyde-based dispersantsand polycarboxylated ether dispersants. One example of a suitablesulfonated-formaldehyde-based dispersant is a sulfonated acetoneformaldehyde condensate, available from Halliburton Energy Services,Inc., as CFR-3™ dispersant. One example of a suitable polycarboxylatedether dispersant is Liquiment® 514L or 5581F dispersants, available fromBASF Corporation, Houston, Tex.

The cement set activator may be added to the set-delayed cementcomposition in an amount sufficient to induce the set-delayed cementcomposition to set into a hardened mass. For example, the cement setactivator may be added to the set-delayed cement composition in anamount in the range of about 0.1% to about 20% by weight of the pumice.In specific examples, the cement set activator may be present in anamount ranging between any of and/or including any of about 0.1%, about1%, about 5%, about 10%, about 15%, or about 20% by weight of thepumice. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of cement setactivator to include for a chosen application.

Other additives suitable for use in subterranean cementing operationsalso may be included in examples of the set-delayed cement compositions.Examples of such additives include, but are not limited to: weightingagents, lightweight additives, mechanical-property-enhancing additives,fluid-loss-control additives, defoaming agents, foaming agents, andcombinations thereof. One or more of these additives may be added to theset-delayed cement compositions after storing but prior to the placementof a set-delayed cement composition into a subterranean formation. Aperson having ordinary skill in the art, with the benefit of thisdisclosure, should readily be able to determine the type and amount ofadditive useful for a particular application and desired result.

Weighting agents may be included in the set-delayed cement compositions.Weighting agents are typically materials that weigh more than water andmay be used to increase the density of the set-delayed cementcompositions. By way of example, weighting agents may have a specificgravity of about 2 or higher (e.g., about 2, about 4, etc.). Examples ofweighting agents that may be used include, but are not limited to,hematite, hausmannite, barite, and combinations thereof. Specificexamples of suitable weighting agents include HI-DENSE® weighting agent,available from Halliburton Energy Services, Inc.

Lightweight additives may be included in the set-delayed cementcompositions, for example, to decrease the density of the set-delayedcement compositions. Examples of suitable lightweight additives include,but are not limited to, bentonite, coal, diatomaceous earth, expandedperlite, fly ash, gilsonite, hollow microspheres, low-density elasticbeads, nitrogen, pozzolan-bentonite, sodium silicate, combinationsthereof, or other lightweight additives known in the art. The resincompositions may generally have lower base densities than theset-delayed cement compositions, thus hollow glass beads and/or foam maybe suitable lightweight additives for the set-delayed cementcompositions, dependent upon the base densities of the set-delayedcement compositions.

Optionally, cement foaming additives may be included in the set-delayedcement compositions, for example, to facilitate foaming and/or stabilizethe resultant foam formed therewith. The foaming additive may include asurfactant or combination of surfactants that reduce the surface tensionof the water. As will be appreciated by those of ordinary skill in theart, the foaming additives may be used in conjunction with a gas toproduce a foamed set-delayed cement compositions. By way of example, thefoaming agent may comprise an anionic, nonionic, amphoteric (includingzwitterionic surfactants), cationic surfactant, or mixtures thereof.Examples of suitable foaming additives include, but are not limited to:betaines; anionic surfactants such as hydrolyzed keratin; amine oxidessuch as alkyl or alkene dimethyl amine oxides; cocoamidopropyldimethylamine oxide; methyl ester sulfonates; alkyl or alkeneamidobetaines such as cocoamidopropyl betaine; alpha-olefin sulfonates;quaternary surfactants such as trimethyltallowammonium chloride andtrimethylcocoammonium chloride; C8 to C22 alkylethoxylate sulfates; andcombinations thereof. Specific examples of suitable foaming additivesinclude, but are not limited to: mixtures of an ammonium salt of analkyl ether sulfate, a cocoamidopropyl betaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride, andwater; mixtures of an ammonium salt of an alkyl ether sulfatesurfactant, a cocoamidopropyl hydroxysultaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride, andwater; hydrolyzed keratin; mixtures of an ethoxylated alcohol ethersulfate surfactant, an alkyl or alkene amidopropyl betaine surfactant,and an alkyl or alkene dimethylamine oxide surfactant; aqueous solutionsof an alpha-olefinic sulfonate surfactant and a betaine surfactant; andcombinations thereof. An example of a suitable foaming additive isZONESEALANT™ 2000 agent, available from Halliburton Energy Services,Inc.

Optionally, set accelerators for the set-delayed cement compositions maybe included in the set-delayed cement compositions, for example, toincrease the rate of setting reactions. Control of setting time mayallow for the ability to adjust to wellbore conditions or customize settimes for individual jobs. Examples of suitable set accelerators mayinclude, but are not limited to, aluminum sulfate, alums, calciumchloride, calcium sulfate, gypsum-hemihydrate, sodium aluminate, sodiumcarbonate, sodium chloride, sodium silicate, sodium sulfate, ferricchloride, or a combination thereof. For example, aluminum sulfate may beused to accelerate the setting time of the set-delayed cementcompositions for surface uses which may require fast setting, forexample, roadway repair, consumer uses, etc. The cement set acceleratorsmay be added alongside any cement set activators when setting of theset-delayed cement compositions is desired. Alternatively, the setaccelerators may be added before the cement set activator if desired,and if the set accelerator does not induce premature setting. Withoutbeing limited by theory, aluminum sulfate may promote the formation ofsulfate containing species (e.g., ettringite) which may modify therheology of the matrix during hydration such that textural uniformityand adherence to a surface is improved. Set accelerators may produce aset-delayed cement composition with a thickening time of less than 10minutes, alternatively less than 5 minutes, alternatively, less than 1minute, or further alternatively less than 30 seconds.

Optionally, mechanical-property-enhancing additives for set-delayedcement compositions may be included in the set-delayed cementcompositions, for example, to ensure adequate compressive strength andlong-term structural integrity. These properties can be affected by thestrains, stresses, temperature, pressure, and impact effects from asubterranean environment. Examples of mechanical-property-enhancingadditives include, but are not limited to, carbon fibers, glass fibers,metal fibers, mineral fibers, silica fibers, polymeric elastomers,latexes, and combinations thereof.

Optionally, fluid-loss-control additives for cement may be included inthe set-delayed cement compositions, for example, to decrease the volumeof fluid that is lost. Properties of the set-delayed cement compositionsmay be significantly influenced by their water content. The loss offluid can subject the set-delayed cement compositions to degradation orcomplete failure of design properties. Examples of suitablefluid-loss-control additives include, but not limited to, certainpolymers, such as hydroxyethyl cellulose, carboxymethylhydroxyethylcellulose, copolymers of 2-acrylamido-2-methylpropanesulfonic acid andacrylamide or N,N-dimethylacrylamide, and graft copolymers comprising abackbone of lignin or lignite and pendant groups comprising at least onemember selected from the group consisting of2-acrylamido-2-methylpropanesulfonic acid, acrylonitrile, andN,N-dimethylacrylamide.

Optionally, cement defoaming additives may be included in theset-delayed cement compositions, for example, to reduce the tendency ofthe set-delayed cement compositions to foam during mixing and pumping ofthe set-delayed cement compositions. Examples of suitable defoamingadditives include, but are not limited to, polyol silicone compounds.Suitable defoaming additives are available from Halliburton EnergyServices, Inc., under the product name D-AIR™ defoamers.

Optionally, fibers may be included in the set-delayed cementcompositions, for example, to enhance the tensile and ductile propertiesthe set-delayed cement compositions. Examples of suitable fibersinclude, but are not limited to, polyvinylalcohol, polypropylene,carbon, glass etc. Further, the fluidic nature and storage capabilitiesof the set-delayed cement composition allow for fibers which may, inother compositions, require high shear and high pressure pumpingconditions for dispersion, to be dispersed using low. This isparticularly advantageous in systems where the fibers may bridge andplug pumping equipment.

Optionally, refractory materials may be included in the set-delayedcement compositions, for example, to provide a set-delayed cementcomposition with higher heat resistance. Examples of suitable refractorymaterials include, but are not limited to, alumina, titanium, fire brickgrog, etc. These refractory materials may be of particular importance inapplications where fire and heat resistance is particularly important,for example, in consumer applications in the home.

The set-delayed cement compositions may possess properties beneficialfor use in concrete applications. For example, in a typical concreteformulation, the aggregate (e.g., chert, quartzite, opal, strainedquartz crystals, etc.) may be dissolved by the basic pore solution ofthe cement in what is known as an alkali silicate reaction. Thedissolved portion of the aggregate may then react with calcium speciespresent in the cement pore solution to form a calcium-silicate-hydrategel. This alkali silicate reaction may be represented by Equation 1below:Ca(OH)₂+H₄SiO₄→Ca²⁺+H₂SiO₄ ²⁻+2H₂O→CaH₂SiO₄.2H₂O  (Eq. 1)The calcium-silicate-hydrate gel formed from the aggregate, effectivelyincreases the size of the aggregate. This increase in size may exert aforce on the surrounding cement that consequently causes cracks ordeformations in the surrounding cement. Without limitation by theory, itis believed that the set-delayed cement compositions may prevent ormitigate any alkali silicate reactions by binding the alkali materialspresent, increasing the tensile strength of the concrete, and/or byreducing the dissolution rate of the aggregate (e.g., the set-delayedcement compositions may have a pore solution pH of 12.5 as compared to apH of 13.2 for standard concrete). Furthermore the set-delayed cementcomposition may be formulated such that the hydrated lime may becompletely consumed by the pumice and thus prevent any initialdissolution of the aggregate.

The set-delayed cement compositions may be used in applications ofspray-applied cement and concrete. Spray-applied cement and concrete maybe used through either a wet process or a dry process. The dry-mixprocess comprises pumping a dry cementitious material through a conduitand adding water at the exit of the conduit. In the wet-mix process, thecementitious material is mixed with water before being loaded into theconduit. When loaded into the conduit, the cement or concrete slurry ispumped to the exit of the conduit (e.g., a nozzle), where it may besprayed onto a target area using compressed gas added at the conduitexit. The set-delayed cement compositions disclosed herein may be usedin wet-mix spray-applications. In particular, the set-delayed cementcomposition may be spray-applied in cementing applications for tunnels,mines, reservoirs, swimming pools, repair works, fire damagedstructures, retaining walls, refractory linings, zoological structures,bridges, dams, and the like. In a specific example, a set-delayed cementcomposition may be prepared in advance and then stored as a stableslurry until needed, whereby the set-delayed cement composition may beloaded into a cement spraying apparatus and sprayed onto a target area.In the aforementioned example, on-site mixing of the cement is no longerneeded and thus the cement may be prepared off-site under strictercontrol standards and conditions.

As previously mentioned, the set-delayed cement compositions may have adelayed set in that they remain in a pumpable fluid state for at leastone day (e.g., at least about 1 day, about 2 weeks, about 2 years ormore) at room temperature (e.g., about 80° F.) in quiescent storage. Forexample, the set-delayed cement compositions may remain in a pumpablefluid state for a period of time from about 1 day to about 7 days ormore. In some examples, the set-delayed cement compositions may remainin a pumpable fluid state for at least about 1 day, about 7 days, about10 days, about 20 days, about 30 days, about 40 days, about 50 days,about 60 days, or longer. A fluid is considered to be in a pumpablefluid state where the fluid has a consistency of less than 70 Beardenunits of consistency (“Bc”), as measured on a pressurized consistometerin accordance with the procedure for determining cement thickening timesset forth in API RP Practice 10B-2, Recommended Practice for TestingWell Cements, First Edition, July 2005.

Those of ordinary skill in the art will appreciate that the set-delayedcement compositions should have a density suitable for a particularapplication. By way of example, the set-delayed cement compositions mayhave a density in the range of from about 4 pounds per gallon (“lb/gal”)to about 20 lb/gal. In certain examples, the set-delayed cementcompositions may have a density in the range of from about 8 lb/gal toabout 17 lb/gal. Examples of the set-delayed cement compositions may befoamed or unfoamed or may comprise other means to reduce theirdensities, such as hollow microspheres, low-density elastic beads, orother density-reducing additives known in the art. In examples, thedensity may be reduced after storing the composition, but prior toplacement in a subterranean formation. Those of ordinary skill in theart, with the benefit of this disclosure, will recognize the appropriatedensity for a particular application. In some examples, the set-delayedcement compositions may set to have a desirable compressive strengthafter activation. Compressive strength is generally the capacity of amaterial or structure to withstand axially directed pushing forces. Thecompressive strength may be measured at a specified time after theset-delayed cement composition has been activated and the resultantcomposition is maintained under specified temperature and pressureconditions. Compressive strength can be measured by either destructiveor non-destructive methods. The destructive method physically tests thestrength of treatment fluid samples at various points in time bycrushing the samples in a compression-testing machine. The compressivestrength is calculated from the failure load divided by thecross-sectional area resisting the load and is reported in units ofpound-force per square inch (psi). Non-destructive methods may employ aUCA™ ultrasonic cement analyzer, available from Fann Instrument Company,Houston, Tex. Compressive strength values may be determined inaccordance with API RP 10B-2, Recommended Practice for Testing WellCements, First Edition, July 2005.

By way of example, the set-delayed cement compositions may develop a24-hour compressive strength in the range of from about 50 psi to about5000 psi, alternatively, from about 100 psi to about 4500 psi, oralternatively from about 500 psi to about 4000 psi. In some examples,the set-delayed cement compositions may develop a compressive strengthin 24 hours of at least about 50 psi, at least about 100 psi, at leastabout 500 psi, or more. In some examples, the compressive strengthvalues may be determined using destructive or non-destructive methods ata temperature ranging from 100° F. to 200° F.

In some examples, the set-delayed cement compositions may have desirablethickening times after activation. Thickening time typically refers tothe time a fluid, such as a set-delayed cement composition, remains in afluid state capable of being pumped. A number of different laboratorytechniques may be used to measure thickening time. A pressurizedconsistometer, operated in accordance with the procedure set forth inthe aforementioned API RP Practice 10B-2, may be used to measure whethera fluid is in a pumpable fluid state. The thickening time may be thetime for the treatment fluid to reach 70 Bc and may be reported as thetime to reach 70 Bc. The thickening time may be modified for anytemperature at atmospheric pressure by modification of the formula,concentration of additives (e.g. activator/accelerator), etc. In someexamples, the set-delayed cement compositions may have a thickening timeat atmospheric pressure and surface temperatures between about 30seconds to about 10 hours. For example, the set-delayed cementcompositions may have a thickening time of greater than about 30seconds, greater than about 1 minute, greater than about 10 minutes,greater than about 1 hour, or greater than about 10 hours.

In some examples, a set-delayed cement composition may be provided thatcomprises water, pumice, hydrated lime, a set retarder, and optionally adispersant. The set-delayed cement composition may be stored, forexample, in a vessel or other suitable container. The set-delayed cementcomposition may be permitted to remain in storage for a desired timeperiod. For example, the set-delayed cement composition may remain instorage for a time period of about 1 day or longer. For example, theset-delayed cement composition may remain in storage for a time periodof about 1 day, about 2 days, about 5 days, about 7 days, about 10 days,about 20 days, about 30 days, about 40 days, about 50 days, about 60days, or longer. In some examples, the set-delayed cement compositionmay remain in storage for a time period in a range of from about 1 dayto about 7 days or longer. Thereafter, the set-delayed cementcomposition may be activated, for example, by addition of a cement setactivator, used in a cementing or concrete application and allowed toset in the course of said application.

A method of spraying a surface with a set-delayed cement composition maybe provided. The method may be used in conjunction with one or more ofthe methods, compositions, and/or systems illustrated in FIGS. 1-4. Themethod may comprise providing a set-delayed cement compositioncomprising water, pumice, hydrated lime, and a set retarder; spraying asurface with the set-delayed cement composition; and allowing theset-delayed cement composition to set on the surface. The set retardermay comprise at least one retarder selected from the group consisting ofa phosphate, a phosphonate, a phosphonic acid, a phosphonic acidderivative, a lignosulfonate, a salt, an organic acid, acarboxymethylated hydroxyethylated cellulose, a synthetic co- orter-polymer comprising sulfonate and carboxylic acid groups, a boratecompound, and any mixture thereof. The set-delayed cement compositionmay further comprise a cement set activator selected from the groupconsisting of a zeolite, amine, silicate, Group IA hydroxide, Group IIAhydroxide, monovalent salt, divalent salt, nanosilica, polyphosphate,and any combination thereof. The set-delayed cement compositioncomprising the cement set activator may further comprise a thickeningtime in a range between about 30 seconds to about 10 minutes. Theset-delayed cement composition may further comprise a fiber. Theset-delayed cement composition may further comprise a dispersantselected from the group consisting of a sulfonated-formaldehyde-baseddispersant, a polycarboxylated ether dispersant, and any combinationthereof. Prior to the spraying step, the set-delayed cement compositionmay be stored for a period of at least about 1 day. The surface may bedisposed about, on, or within a mine, a pond, a creek, a river, theocean floor, a beach shore, a wall, a ceiling, a floor, an attic, or abasement. The set-delayed cement composition may be disposed within amine and wherein the set-delayed cement composition may be pumped from avessel outside of the mine into the mine. The set-delayed cementcomposition may be foamed. The set-delayed cement composition maycomprise refractory materials. The set-delayed cement composition maycomprise a dye and/or beads.

A method of coating a surface with a set-delayed cement composition maybe provided. The method may be used in conjunction with one or more ofthe methods, compositions, and/or systems illustrated in FIGS. 1-4. Themethod may comprise providing a set-delayed cement compositioncomprising water, pumice, hydrated lime, and a set retarder; coating asurface with the set-delayed cement composition; and allowing theset-delayed cement composition to set on the surface. The set retardermay comprise at least one retarder selected from the group consisting ofa phosphate, a phosphonate, a phosphonic acid, a phosphonic acidderivative, a lignosulfonate, a salt, an organic acid, acarboxymethylated hydroxyethylated cellulose, a synthetic co- orter-polymer comprising sulfonate and carboxylic acid groups, a boratecompound, and any mixture thereof. The set-delayed cement compositionmay further comprise a cement set activator selected from the groupconsisting of a zeolite, amine, silicate, Group IA hydroxide, Group IIAhydroxide, monovalent salt, divalent salt, nanosilica, polyphosphate,and any combination thereof. The set-delayed cement compositioncomprising the cement set activator may further comprise a thickeningtime in a range between about 30 seconds to about 10 minutes. Theset-delayed cement composition may further comprise a fiber. Theset-delayed cement composition may further comprise a dispersantselected from the group consisting of a sulfonated-formaldehyde-baseddispersant, a polycarboxylated ether dispersant, and any combinationthereof. Prior to the coating step, the set-delayed cement compositionmay be stored for a period of at least about 1 day. The surface may bedisposed about, on, or within a mine, a pond, a creek, a river, theocean floor, a beach shore, a wall, a ceiling, a floor, an attic, or abasement. The set-delayed cement composition may be disposed within amine and wherein the set-delayed cement composition may be pumped from avessel outside of the mine into the mine. The set-delayed cementcomposition may be foamed. The set-delayed cement composition maycomprise refractory materials. The set-delayed cement composition maycomprise a dye and/or beads. Coating a surface with the set-delayedcement composition may comprise painting the surface with theset-delayed cement composition or dipping the surface into a vesselcontaining the set-delayed cement composition

A cementing system may be provided. The system may be used inconjunction with one or more of the methods, compositions, and/orsystems illustrated in FIGS. 1-4. The system may comprise a set-delayedcement composition comprising: water, pumice, hydrated lime, and a setretarder, wherein the set-delayed cement composition is capable ofremaining in a pumpable fluid state for at least about one day at 80°F.; a cementing unit comprising: a vessel, a conduit; and a nozzlecoupled to the conduit. The cementing unit may further comprise apneumatic system comprising a gas compressor, a compressed gas, and acompressed gas conduit, wherein the compressed gas conduit is coupled tothe nozzle, and wherein the compressed gas is capable of spraying theset-delayed cement composition. The nozzle may comprise an applicatorcapable of applying a cement set activator to the set-delayed cementcomposition. The cementing unit may further comprise a hydraulic systemcoupled to the nozzle, wherein the hydraulic system may be capable ofspraying the set-delayed cement composition. The set retarder maycomprise at least one retarder selected from the group consisting of aphosphate, a phosphonate, a phosphonic acid, a phosphonic acidderivative, a lignosulfonate, a salt, an organic acid, acarboxymethylated hydroxyethylated cellulose, a synthetic co- orter-polymer comprising sulfonate and carboxylic acid groups, a boratecompound, and any mixture thereof. The set-delayed cement compositionmay further comprise a cement set activator selected from the groupconsisting of a zeolite, amine, silicate, Group IA hydroxide, Group IIAhydroxide, monovalent salt, divalent salt, nanosilica, polyphosphate,and any combination thereof. The set-delayed cement compositioncomprising the cement set activator may further comprise a thickeningtime in a range between about 30 seconds to about 10 minutes. Theset-delayed cement composition may further comprise a fiber. Theset-delayed cement composition may further comprise a dispersantselected from the group consisting of a sulfonated-formaldehyde-baseddispersant, a polycarboxylated ether dispersant, and any combinationthereof. The set-delayed cement composition may be foamed. Theset-delayed cement composition may comprise refractory materials. Theset-delayed cement composition may comprise a dye and/or beads.

Referring now to FIG. 1, the preparation of a set-delayed cementcomposition in accordance with the examples described herein will now bedescribed. FIG. 1 illustrates a fluid handling system 2 for thepreparation of a set-delayed cement composition and subsequent deliveryof the composition to a cementing application site. As shown, theset-delayed cement composition may be mixed and/or stored in a vessel 4.Vessel 4 may be any such vessel suitable for containing and/or mixingthe set-delayed cement composition, including, but not limited to drums,barrels, tubs, bins, jet mixers, re-circulating mixers, batch mixers,and the like. The set-delayed cement composition may then be pumped viapumping equipment 6. In some embodiments, the vessel 4 and the pumpingequipment 6 may be disposed on one or more cementing units (e.g.,cementing unit 8 as shown on FIG. 2) as will be apparent to those ofordinary skill in the art. In some embodiments, a jet mixer may be used,for example, to continuously mix the lime/settable material with thewater as it is being pumped to the wellbore. In set-delayed embodiments,a re-circulating mixer and/or a batch mixer may be used to mix theset-delayed cement composition, and the activator may be added to themixer as a powder prior to pumping the cement composition downhole.Additionally, batch mixer type units for the slurry may be plumbed inline with a separate tank containing a cement set activator. The cementset activator may then be fed in-line with the slurry as it is pumpedout of the mixing unit. Further, in embodiments requiring a concrete,aggregate may be mixed with the set-delayed cement composition in vessel4 before being pumped via pumping equipment 6

FIG. 2 illustrates the use of the set-delayed cement composition in aspraying application. Cementing unit 8, which may comprise vessel 4 andpumping equipment 6 as described in FIG. 1, may be used to spray aset-delayed cement composition on a rock lined pond bed 10. Cementingunit 8 may comprise a vessel capable of storing a set-delayed cementcomposition (e.g., vessel 4) and/or equipment used to deliver aset-delayed cement composition to a job site, illustrated by pumpingequipment 6 and conduit 12. As illustrated by FIG. 2, rock lined pondbed 10 may comprise pores, voids, gaps, etc. that may make permeable andprone to erosion. Due to the inherent nature of the set-delayed cementcomposition, the set-delayed cement composition may be delivered throughconduit 12 and sprayed onto rock lined pond bed 10 using a pneumaticsystem comprising gas compressor 14 and compressed gas conduit 16, whichmay be utilized to spray the set delayed cement composition from nozzle18. Alternatively, the spraying may be accomplished by a hydraulicsystem (not shown), for example, comprising an incompressible liquid toexert a direct or indirect force on the set-delayed cement compositionsuch that the set-delayed cement composition may be sprayed from an exitin the conduit 12. Once sprayed, the set-delayed cement composition maybe activated for use by a cement set activator, alternatively anapplicator within the nozzle 18 of conduit 12 may apply the cement setactivator as it exits nozzle 18 as shown in the inset of FIG. 2.Applicator 20 may comprise an opening and a valve through whichactivator conduit 22 may convey cement set activator to nozzle 18 whereit may mix with a set-delayed cement composition in conduit 12.Additionally, activator pump 24 my pump cement set activator throughactivator conduit 22. The activated set-delayed cement composition maythen be sprayed from the nozzle 18 using the compressed gas carried tonozzle 18 via compressed gas conduit 16. The strength of the cement setactivator may be adjusted to adjust the thickening time of theset-delayed cement composition. The strength may be adjusted by using arelatively stronger cement set activator and/or also by increasing thecement set activator concentration. For example, a higher concentrationof more reactive cement set activator may be used to induce setting ofthe set-delayed cement as soon as it is applied to a surface. Similarly,the set-delayed cement composition may be used in applications where thelining of porous or erosion prone structures would be desired. Forexample, the set-delayed cement composition may be used on ponds,reservoirs, drainage ditches, creek beds, rivers banks, and the like.Once set, the set-delayed cement composition may prevent leakage and/orerosion through and within the covered surfaces.

FIG. 3 illustrates a marine construction application, wherein aset-delayed cement composition may be pumped through conduit 12 tosecure in place a beam 28 to be used in the extension of pier 26. Theset-delayed cement composition may be sprayed from nozzle 18 using apneumatic system, for example, one comprising compressed gas fromcompressed gas conduit 16. Alternatively, the spraying may beaccomplished by a hydraulic system (not shown), for example, comprisingan incompressible liquid to exert a direct or indirect force on theset-delayed cement composition such that the set-delayed cementcomposition may be sprayed from an exit in the conduit 12. As discussedabove, the set-delayed cement composition is capable of extended storagewherein it remains in a stable fluid, slurry state until activated bythe addition of a suitable cement set activator and allowed to set toform set cement 30. Set cement 30 is a set-delayed cement compositionthat has been activated and allowed to set in place. As such, theset-delayed cement composition may be placed near a location or removedto a logistically convenient position and pumped to a desired area. Thecement set activator may be added while mixing the set-delayed cementcomposition prior to pumping, or may added while pumping the set-delayedcement composition, for example, through an applicator within the nozzleof conduit 10. Set-delayed cement composition may be well suited formarine environments and may be particularly advantageous in deep-waterscenarios due to its simplified delivery mechanism, reduced transportrisk, and easier logistics since powder transport and mixing are notrequired.

FIG. 4 illustrates the use of a set-delayed cement composition for mineconstruction/repair. Cementing unit 8, which may comprise vessel 4,pumping equipment 6, and conduit 12, may be used to store, mix, andtransport a set-delayed cement composition into a mine or otherunderground structure where it may be difficult to transport equipment.As illustrated by FIG. 4, the bulk of the cementing equipment and theset-delayed cement composition may be stored above ground. When desired,the set-delayed cement composition may be pumped by cementing unit 8 viaconduit 12 to the underground job site where the set-delayed cementingcomposition may be used to consolidate, seal, or reinforce thetunnel/mine structure. Thus, transport time and or size constraintissues of the cementing equipment may be reduced or eliminated. Theset-delayed cement composition may be poured from conduit 12 or it maybe sprayed using a pneumatic system, for example, one comprisingcompressed gas from gas compressor 14 and compressed gas conduit 16.Alternatively, the spraying may be accomplished by a hydraulic system(not shown), for example, comprising an incompressible liquid to exert adirect or indirect force on the set-delayed cement composition such thatthe set-delayed cement composition may be sprayed from an exit in theconduit 12. With the benefit of this disclosure, one of ordinary skillin the art will be able to determine the best method of applying aset-delayed cement and/or concrete.

Additional examples may comprise using the set-delayed cementcomposition for coating applications. In these examples, a coating maybe applied by spraying, painting, rolling-on dipping, etc. The coatingmay be applied to decorative or structural purposes. The set-delayedcement composition may be easily dyed and can be formulated to provide afast-setting adhesive coating of a desirable color. The coating may beused to aesthetically enhance walls, floors, ceilings, sculptures, orany such desirable structure. Further, ornamental aggregate may be addedto the set-delayed cement composition for additional aesthetic effects.Ornamental aggregate may comprise glitter, beads, and the like.

Additionally, the set-delayed cement compositions may provide a heatresistant coating to a surface. The disclosed set-delayed cementcomposition is stable up to temperatures as high as 400° F. Therefore,coating a surface with the set-delayed cement compositions disclosedherein may impart a heat resistant coating to the surface. Further, asdiscussed above, heat refractory materials may be added to theset-delayed cement compositions to increase the heat resistance of theset-delayed cement compositions. Such materials may comprise, but arenot limited to, alumina, titanium, fire brick grog, and the like.

Further, the set-delayed cement compositions may be foamed. Theset-delayed cement composition may be formed using a foaming additive asdescribed above or a pressurized gas. Equipment, such as fluid handlingsystem 2 (as shown in FIG. 1) or cementing unit 8 (as shown in FIGS. 2and 4), may be used to continuously produce foamed set-delayed cementcomposition that may be sprayed or coated onto a targeted surface whereit may remain in place due to the rheology of the foamed set-delayedcement composition. Optionally, the foamed set-delayed cementcomposition may be passed through a heat exchanger and/or supplied acement set accelerator to accelerate the setting process. The foamedset-delayed cement composition may be used in many applications. Anexample of an application comprises a fire retardant insulation whichmay be applied to many types of surfaces.

The exemplary set-delayed cement compositions disclosed herein maydirectly or indirectly affect one or more components or pieces ofequipment associated with the preparation, delivery, recapture,recycling, reuse, and/or disposal of the disclosed set-delayed cementcompositions. For example, the disclosed set-delayed cement compositionsmay directly or indirectly affect one or more mixers, related mixingequipment, mud pits, storage facilities or units, compositionseparators, heat exchangers, sensors, gauges, pumps, compressors, andthe like used generate, store, monitor, regulate, and/or recondition theexemplary set-delayed cement compositions. The disclosed set-delayedcement compositions may also directly or indirectly affect any transportor delivery equipment used to convey the set-delayed cement compositionsto a well site or downhole such as, for example, any transport vessels,conduits, pipelines, trucks, tubulars, and/or pipes used tocompositionally move the set-delayed cement compositions from onelocation to another, any pumps, compressors, or motors (e.g., topside ordownhole) used to drive the set-delayed cement compositions into motion,any valves or related joints used to regulate the pressure or flow rateof the set-delayed cement compositions, and any sensors (i.e., pressureand temperature), gauges, and/or combinations thereof, and the like. Thedisclosed set-delayed cement compositions may also directly orindirectly affect the various downhole equipment and tools that may comeinto contact with the set-delayed cement compositions such as, but notlimited to, wellbore casing, wellbore liner, completion string, insertstrings, drill string, coiled tubing, slickline, wireline, drill pipe,drill collars, mud motors, downhole motors and/or pumps, cement pumps,surface-mounted motors and/or pumps, centralizers, turbolizers,scratchers, floats (e.g., shoes, collars, valves, etc.), logging toolsand related telemetry equipment, actuators (e.g., electromechanicaldevices, hydromechanical devices, etc.), sliding sleeves, productionsleeves, plugs, screens, filters, flow control devices (e.g., inflowcontrol devices, autonomous inflow control devices, outflow controldevices, etc.), couplings (e.g., electro-hydraulic wet connect, dryconnect, inductive coupler, etc.), control lines (e.g., electrical,fiber optic, hydraulic, etc.), surveillance lines, drill bits andreamers, sensors or distributed sensors, downhole heat exchangers,valves and corresponding actuation devices, tool seals, packers, cementplugs, bridge plugs, and other wellbore isolation devices, orcomponents, and the like.

EXAMPLES

To facilitate a better understanding of the present embodiments, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, theentire scope of the embodiments.

Example 1

The following series of tests was performed to evaluate the forceresistance properties of comparative cement compositions comprisingpumice and hydrated lime. Three different comparative sample settablecompositions, designated Samples 1-3, were prepared using pumice (DS-325lightweight aggregate), hydrated lime, Liquiment® 514L dispersant, andwater, as indicated in the table below. After preparation, the sampleswere placed in an UCA and cured at 140° F. and 3,000 psi for 24 hours.The cured cement was then removed from the UCA and crushed to yield thecompressive strength values provided in Table 1 below.

TABLE 1 Compressive Strength Tests Sample 1 2 3 Density lb/gal 14.3 14.314.3 Pumice:Lime Wt. Ratio 3:1 4:1 5:1 Pumice g 400 400 400 Lime g 134103 100 Dispersant g 12 4 13 Water g 196 187 220 24-Hr Crush Strengthpsi 2,240 1,960 2,130

Example 1 thus indicates that cement compositions that comprise pumiceand lime in a weight ratio ranging from 3:1 to 5:1 may developcompressive strengths suitable for particular applications.

Example 2

A sample set-delayed cement composition, designated Sample 4, having adensity of 13.3 lb/gal was prepared that comprised 500 grams of pumice(DS-325 lightweight aggregate), 100 grams of hydrated lime, 13 grams ofLiquiment® 514L dispersant, 24 grams of Micro Matrix® cement retarder,and 300 grams of water. The rheological properties of the sample weremeasured after storing at room temperature and pressure for periods of 1day and 6 days. After preparation, the rheological properties of thesample were determined at room temperature (e.g., about 80° F.) using aModel 35A Fann Viscometer and a No. 2 spring, in accordance with theprocedure set forth in API RP Practice 10B-2, Recommended Practice forTesting Well Cements. The results of this test are set forth in thetable below.

TABLE 2 Viscosity Tests Age of Yield Plastic Sample Fann Readings PointViscosity (days) 600 300 200 100 6 3 (lb/100 ft²⁾ (centipoise) 1 560 322244 170 46 38 84 238 6 498 310 228 136 24 20 122 188

Example 2 thus indicates that set-delayed cement compositions thatcomprise pumice, hydrated lime, a dispersant, a set retarder, and watercan remain fluid after 6 days.

Example 3

A sample set-delayed cement composition, designated Sample 5, having adensity of 13.4 lb/gal was prepared that comprised 500 grams of pumice(DS-325 lightweight aggregate), 100 grams of hydrated lime, 7 grams ofLiquiment® 514L dispersant, 6.3 grams of Micro Matrix® cement retarder,and 304 grams of water. The rheological properties of the sample weremeasured after storing at room temperature and pressure for periods offrom 1 day to 19 days. The rheological properties were measured at roomtemperature (e.g., about 80° F.) using a Model 35A Fann Viscometer and aNo. 2 spring, in accordance with the procedure set forth in API RPPractice 10B-2, Recommended Practice for Testing Well Cements. Theresults of this test are set forth in the table below.

TABLE 3 Viscosity Tests Age of Sample Fann Readings (Days) 300 200 100 63 1 462 300 130 12 8 2 458 282 122 6 4 5 420 260 106 3 2 8 446 270 110 41 12 420 252 100 3 2 19 426 248 94 2 1

After 7 days, calcium chloride in the amount indicated in Table 4 belowwas added to a separately prepared sample of the same formulation asabove. The sample was then placed in an UCA and the initial settingtime, which is the time for the composition to reach a compressivestrength of 50 psi while maintained at 3,000 psi was determined inaccordance with API RP Practice 10B-2, Recommended Practice for TestingWell Cements. The initial setting time of the sample was also determinedwithout addition of the calcium chloride. The samples with and withoutthe calcium chloride were heated to a temperature of 140° F. in 30minutes and then maintained at that temperature throughout the test.

TABLE 4 Compressive Strength Tests CaCl₂ Age of Test (% by wt of SampleTemperature Pumice & Initial Setting Time (Days) (° F.) Lime) (hr:min) 7140 0 no set after 4 days 7 140 10 5:11

Example 3 thus indicates that the set-delayed cement compositions thatcomprise pumice, hydrated lime, a dispersant, a set retarder, and waterwill not set for a period of at least 19 days at ambient temperature andover 4 days at 140° F. Example 3 further indicates that sampleset-delayed cement compositions may be activated at a desired time byaddition of a suitable activator.

Example 4

A sample set-delayed cement composition, designated Sample 6, having adensity of 13.4 lb/gal was prepared that comprised pumice (DS-325lightweight aggregate), 20% hydrated lime, 1.4% Liquiment® 514Ldispersant, 1.26% Micro Matrix® cement retarder, and 62% of water (allby weight of pumice, referred to in the table below as “% bwop”). After45 days in storage at ambient conditions, the sample was mixed with 6%calcium chloride. At 140° F., the sample had a thickening time (time to70 BC) of 2 hours and 36 minutes and an initial setting time (time to 50psi) of 9 hours and 6 minutes as measured using an UCA while maintainedat 3000 psi. After 48 hours, the sample was crushed with a mechanicalpress which gave a compressive strength of 2,240 psi. The thickeningtime and initial setting time were both determined in accordance withAPI RP Practice 10B-2, Recommended Practice for Testing Well Cements.The results of this test are set forth in the table below.

TABLE 5 Compressive Strength Tests Initial 48 Hr Age of Test CalciumThickening Setting Crush Sample Temperature Chloride Time Time Strength(Days) (° F.) (% bwop) (hr:min) (hr:min) (psi) 45 140 6 2:36 9:36 2,240

Example 4 thus indicates that the set-delayed cement compositions thatcomprise pumice, hydrated lime, a dispersant, a set retarder, and waterwill not set for a period of at least 45 days at ambient temperature.Example 4 further indicates that sample set-delayed cement compositionsmay be activated at a desired time by addition of a suitable activator.

Example 5

This example was performed to evaluate the ability of sodium hydroxideand sodium sulfate to activate a set-delayed cement composition thatcomprised pumice (DS-325 lightweight aggregate), hydrated lime,Liquiment® 514L dispersant, Micro Matrix® cement retarder, and water.Four sample set-delayed cement compositions, designated Samples 7-10,were prepared having concentrations of components as indicated in thetable below. The samples were monitored via an UCA. After the sampleswere placed in the UCA, the pressure was increased to 3,000 psi, and thetemperature was increased to 100° F. over a 15-minute time period andheld for the duration of the test. A portion of the slurry was retainedand poured into a plastic cylinder to monitor the slurry behavior atroom temperature and pressure. These procedures were repeated for allsamples.

Sample 7 was monitored for 72 hours over which time no strength wasdeveloped and the slurry was still pourable when removed from the UCA.The portion kept at room temperature and pressure was likewise stillpourable after 72 hours.

Sample 8 was prepared using the same slurry design as Sample 7 exceptthat sodium hydroxide was added as an activator. The sodium hydroxidewas added in solid form directly to the mixing jar that contained theprepared sample. As can be seen from Table 6, Sample 8, reached 50 psiof compressive strength at 16 hours and 36 minutes. The strengthcontinued to build, reaching a maximum of 1,300 psi, when the test wasstopped at 72 hours. The cured cement was removed from the UCA andcrushed with a mechanical press which gave a compressive strength of 969psi. The portion kept at room temperature and pressure was crushed after7 days resulting in a compressive strength of 143 psi.

Sample 9 was prepared using the same slurry design as Sample 8 exceptthat sodium sulfate was added as an activator. The sodium sulfate wasadded in solid form directly to the mixing jar that contained theprepared slurry. Sample 9 reached 50 psi of compressive strength at 67hours and 29 minutes. The strength continued to build, slowly, reachinga maximum of 78 psi, when the test was stopped at 72 hours. The curedcement was removed from the UCA and crushed with a mechanical presswhich gave a compressive strength of 68.9 psi. The portion kept at roomtemperature and pressure was still too soft to be crushed after 7 days.

Sample 10 was prepared using the same slurry design as Sample 8 exceptthat equal amounts of sodium hydroxide and sodium sulfate were added asan activator. The sodium hydroxide and sodium sulfate were added insolid form directly to the mixing jar that contained the preparedslurry. Sample 10 reached 50 psi of compressive strength at 22 hours and40 minutes. The strength continued to build, reaching a maximum of 900psi, when the test was stopped at 72 hours. The cured cement was removedfrom the UCA and crushed with a mechanical press which gave acompressive strength of 786 psi. The portion kept at room temperatureand pressure was crushed after 7 days resulting in a compressivestrength of 47.9 psi.

The results of these tests are set forth in the table below. Theabbreviation “% bwop” refers to the percent of the component by weightof the pumice. The abbreviation “gal/sk” refers to gallons of thecomponent per 46-pound sack of the pumice. The abbreviation “RTP” refersto room temperature and pressure.

TABLE 6 Compressive Strength Tests Sample 7 8 9 10 Density lb/gal 13.3813.38 13.38 13.38 Water % bwop 61.97 63.60 64.62 64.11 Pumice % bwop 100100 100 100 Hydrated Lime % bwop 20 20 20 20 Dispersant gal/sk 0.07 0.070.07 0.07 Set Retarder % bwop 0.06 0.06 0.06 0.06 Sodium % bwop — 4 — 2Hydroxide Sodium Sulfate % bwop — — 4 2 UCA Temp/Press F/Psi 100/3000100/3000 100/3000 100/3000 Initial Set hr:min >78 16:36 67:29 22:40 (50psi) Final Set hr:min — 21:08 — 32:44 (100 psi) 24 Hr Comp. psi — 138.74— 59.60 Strength 48 Hr Comp. psi — 711.35 — 331.48 Strength 72 Hr Comp.psi — 1300 78 900 Strength 72 Hr Crush psi — 969 68.90 786 Strength(UCA) 7-Day Crush psi — 143.20 0.00 47.90 Strength (RTP)

Example 5 thus indicates that sodium hydroxide, sodium sulfate, andcombinations of the two can activate the set-delayed cementcompositions, but to varying degrees. The testing showed that bothsodium hydroxide and combinations of sodium hydroxide with sodiumsulfate activated the cement compositions to an acceptable level. Whencompared to the non-activated composition, sodium sulfate activated thecement compositions, but much less so than the sodium hydroxide orcombination of sodium hydroxide and sodium sulfate.

It should be understood that the compositions and methods are describedin terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited. Additionally, whenever a numerical range with alower limit and an upper limit is disclosed, any number and any includedrange falling within the range are specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues even if not explicitly recited. Thus, every point or individualvalue may serve as its own lower or upper limit combined with any otherpoint or individual value or any other lower or upper limit, to recite arange not explicitly recited.

Therefore, the present embodiments are well adapted to attain the endsand advantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent embodiments may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Although individual embodiments arediscussed, all combinations of each embodiment are contemplated andcovered by the disclosure. Furthermore, no limitations are intended tothe details of construction or design herein shown, other than asdescribed in the claims below. Also, the terms in the claims have theirplain, ordinary meaning unless otherwise explicitly and clearly definedby the patentee. It is therefore evident that the particularillustrative embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of thepresent disclosure. If there is any conflict in the usages of a word orterm in this specification and one or more patent(s) or other documentsthat may be incorporated herein by reference, the definitions that areconsistent with this specification should be adopted.

What is claimed is:
 1. A cementing method comprising: providing aset-delayed cement composition comprising: water, pumice, hydrated lime,a set retarder, wherein the set-delayed cement composition is capable ofremaining in a pumpable fluid state for at least about one day at 80°F.; providing a cementing unit comprising: a vessel, a first pumpcoupled to the vessel, a first conduit coupled to the vessel, and anozzle coupled to the first conduit, a second pump, a second conduitcoupled to the nozzle and the second pump, an applicator coupled to thenozzle, the applicator comprising an opening and a valve; and apneumatic system comprising a gas compressor, a compressed gas, and acompressed gas conduit, wherein the compressed gas conduit is coupled tothe nozzle, and wherein the compressed gas is capable of spraying theset-delayed cement composition; and using the cementing unit to spraythe set-delayed cement composition.
 2. The cementing method of claim 1,wherein the second conduit is further coupled to the applicator.
 3. Thecementing method of claim 1, wherein the first conduit is handheld. 4.The cementing method of claim 1, wherein the second conduit is separatefrom the first conduit.
 5. The cementing method of claim 1, wherein thesecond conduit extends through the applicator and into the nozzle. 6.The cementing method of claim 1, further comprising spraying theset-delayed cement composition with the cementing unit.
 7. The cementingmethod of claim 1, further comprising providing a cement set activator,wherein at least a portion of the cement set activator is disposedwithin the second conduit.
 8. The cementing method of claim 7, furthercomprising spraying the cement set activator with the cementing unit.